A Functional MRI Study on the Brain Activation Associated with Mental Calculation

ABSTRACT

PURPOSE: In order to investigate the functional brain anatomy associated with mental calculation, functional magnetic resonance imaging was performed. MATERIALS AND METHODS: In six normal right handed subjects, functional MR images were obtained using a 1.5T MR scanner and the EPI BOLD technique. The study included experiment I and experiment II. Each experiment consisted of five resting and four activation periods with each period of 30 seconds. During the activation period of both experiment I and II, calculation equations[an example (4+5)x 8=72] were presented and the subjects were instructed to decide true or false of them. During the resting period of experiment I, the subjects were instructed to visually fixate on a crosshair. During the resting period of experiment II, two diagrams(an example circle, square) were presented and the subjects were instructed to decide they are same or not. For the post-processing of images, the SPM program was used, with the threshold of significance set at p<0.00001. The activated areas during the tasks were assessed. RESULTS: In experiment I, the inferior frontal gyrus, prefrontal cortex, premotor area, supplementary motor area, and intraparietal sulcus including superior parietal cortex were activated bilaterally. Although these areas were also activated in experiment II, the activated signals in the right frontal and parietal lobes were lessened. CONCLUSION: The left inferior frontal gyrus and prefrontal cortex and bilateral intraparietal sulci were activated during mental calculation. The right frontal and parietal lobes might be related to attention and decision making.